1. Technical Field
The present disclosure relates generally to operation within heterogeneous wireless systems such as, for example, hybrid network operation in which client devices can communicate using any one of several networks. More particularly, in one exemplary embodiment, methods and apparatus for synchronizing operational state during hybrid network operation are disclosed.
2. Description of Related Technology
A wireless network operator provides mobile telecommunications services to the public via a network infrastructure. For example, in the exemplary case of cellular systems, the infrastructure includes, inter alia, cellular base stations (BS), base station controllers, infrastructure or distribution nodes, etc. There are a wide variety of cellular network technologies, and historically cellular devices have been specialized for operation within a single cellular network. However, as cellular technologies have become increasingly commoditized, devices are now able to offer so-called “multimode” operation; i.e., a single device that is capable of operation on two or more cellular networks. Multimode operation allows a device to operate on any one of several network technologies, but does not enable operation on multiple network technologies simultaneously.
Incipient research is directed to so-called “hybrid” network operation. During hybrid network operation, the client device operates simultaneously among multiple distinct networks having different technologies. In one exemplary cellular-related case, a hybrid device can support both: (i) Long Term Evolution (LTE) and (ii) Code Division Multiple Access 1× (CDMA 1×) networks; i.e., the device can maintain a simultaneous connection between a first LTE network and a second CDMA 1× network. For example, a LTE/CDMA 1× hybrid device can conduct a voice call over the CDMA 1× network, while the mobile device is in LTE mode for data reception or transmission. In another exemplary case, a hybrid device can support both: (i) CDMA 1×-EVDO (Evolution Data Optimized) and (ii) CDMA 1× networks.
Existing solutions for hybrid network operation rely on the client device to manage its own operation between networks. Specifically, the client device is responsible for maintaining its active connections to the various service networks; there are no required changes to existing network installations (i.e., hybrid network operation does not affect the legacy hardware and software of the network infrastructure). Client-centric hybrid operation has several benefits. For example, there is very little (if any) infrastructure cost for the network operator. Moreover, hardware costs can be incorporated into the price of consumer devices. Additionally, hybrid network operation will not affect existing legacy devices. Similarly, devices capable of hybrid operation are also capable of normal operation.
However, since existing solutions for hybrid network operation do not require the constituent networks to coordinate with one another, the client device will inevitably experience certain scheduling collisions. For example, while a mobile device is attached to a first LTE network, it must periodically “tune out” or “tune away from” the LTE network to perform CDMA 1× actions (such as decoding the Quick Paging Channel (QPCH) to determine if the device is being paged). During the tune-away, the device cannot receive or transmit on the first network (in this example, LTE). If the mobile device is receiving data from the LTE network during the tune out period, this data may be lost.
Certain types of signaling messages control device state. For example, within the context of LTE networks, the mobile device needs to maintain several Radio Resource Control (RRC) and Non-Access Stratum (NAS) timers to avoid and/or properly recover from loss of state synchronization with the network. RRC signaling controls device operation; a mobile device in RRC connected mode has significantly different behavior from a mobile device in RRC idle mode. Consequently, if a device misses an RRC message, the network and the mobile device may lose synchronization, and will have different expectations on signaling and capabilities (e.g., a mobile device may attempt a data transfer on an RRC connection which is non-existent, a mobile device may be operating on stale resource allocations, etc.).
Hence, improved apparatus and methods are needed for mobile device hybrid operation which avoid loss of active communication links (including loss of critical messages and/or synchronization of processes), and which avoids unnecessary or improper operations from occurring within the mobile device as a result of such losses.